Myotonic dystrophy, type 1 is an inherited disorder of the muscles and other body systems. Type 1 myotonic dystrophy tends to be more severe than type 2, and the two forms are caused by mutations in different genes. Myotonic dystrophy, type 1 is a subtype of myotonic dystrophy. Signs and symptoms of this disorder include progressive muscle wasting and weakness, prolonged muscle contractions (myotonia), clouding of the lens of the eye (cataracts), heart abnormalities, balding, and infertility. For additional information, please see the myotonic dystrophy summary. A variation of this disorder, congenital myotonic dystrophy, is evident at birth. The signs and symptoms, which can be severe or life-threatening, include generalized weakness, decreased muscle tone, club foot, difficulty with breathing, developmental delays, and mental retardation.